Off the coast of La Jolla, kelp beds shifted in the surf, their mossy gold fronds twisting down to thick stalks in an underwater grove.

This is California’s other forest, an aquatic counterpart to the state’s storied redwood groves. Like the old growth stands, giant kelp stretch from lush canopies to luminous understories, brimming with life. And like those ancient groves, they face an uncertain future in a changing world.

On a sunny Saturday last month, Ed Parnell, a researcher with Scripps Institution of Oceanography, dove down to take stock of their condition. His conclusion: for the moment, they’re better than expected, and better than other parts of the state.

“It looked a little beat up from the storms, but not as bad as I thought it would be,” said Parnell, who studies kelp ecosystems. “Not as bad as it was a few years ago.”

In Northern California, armies of sea urchins have clear-cut most of the kelp forest, forming “urchin barrens" on the denuded sea floor. Giant kelp off San Diego have fared a bit better, and are recovering from damage wrought by strong storms and abnormally warm water in recent years, Parnell said.

With another El Nino in the works, and ocean temperatures on the rise, however, they could face renewed threats.

“The California Current definitely has changed, and it’s going to continue to change with global warming,” Parnell said. “What that will mean is that we’ll probably lose our kelp forest, and it will change from a forest, to patches that appear and disappear.”

San Diego kelp started dying back around 2014, when “The Blob,” a mass of stagnant warm water, squatted off the Pacific Coast. Kelp rely on upwelling of nutrients from cold water to sustain their stratospheric growth rate, so they withered in the sluggish bath.

The Blob rolled into an El Nino weather pattern in 2015 and 2016, bringing more warm water, along with pounding storms that ripped kelp strands from their holdfasts on the seafloor.

“During strong El Ninos, it’s a double whammy for kelp,” Parnell said. “You have warm water with low nutrients, so the kelp can’t grow. Then you get strong waves that come and wash it out.”

Kelp evolved with those cycles, and has adapted to rugged coastal conditions by maintaining extraordinary productivity, growing up to two feet per day to a maximum length of about 175 feet. A single kelp can live eight to 10 years, but most are torn from their riggings within a year, Parnell said, and quickly replaced by new growth.

“It came back fast,” he said of the kelp’s recovery off La Jolla. “It makes its living by growing fast.”

Andrew Roe

Scripps Institution of Oceanography Researcher Ed Parnell inspects the kelp forest off the San Diego coast during a dive to check on the current conditions of the local kelp.

Scripps Institution of Oceanography Researcher Ed Parnell inspects the kelp forest off the San Diego coast during a dive to check on the current conditions of the local kelp. (Andrew Roe)

On the sunny afternoon, giant kelp floated in greenish-brown masses on the water’s surface, so thick that they tangle around a swimmer. Unlike its terrestrial counterparts in California forests, giant kelp isn’t a plant. Scientifically called Macrocystis pyrifera, it’s a protist, part of the algae kingdom, and the very largest among its clan.

Viewed from underneath, the blades form a gilded canopy on the water’s surface. Gazing down, the stems descend through layers of shimmering blue to the holdfast, which anchors the organism to the sea floor.

The water was a bracing 62 degrees Fahrenheit at the surface, and in the mid-50’s on the ocean floor, so Parnell donned a dry suit to insulate himself from the chilly water. Only a few creatures stirred at the surface; a surf perch flitted through the kelp, while an orange Norrisia norrisii snail and a large barnacle clung to the blades.

The bottom, however, was full of big fish and other organisms. The divers saw kelp bass, sheephead and a four-foot giant seabass, listed as critically endangered on the International Union for Conservation of Nature’s Red List of threatened species. Seeing a big one off San Diego is a good sign, Parnell said. One of his diving companions, his former colleague Cleridy Lennert-Cody, spotted a seven-gill shark, as well.

Giant kelp is a “keystone species” that forms the basis for an entire ecosystem, creating one of the most diverse marine habitats. Steve Schroeter, a research ecologist at UC Santa Barbara, who works in San Diego County, has tallied that diversity while monitoring the kelp bed off of San Dieguito Lagoon.

“Our crew counts about 350 species of invertebrates that live in the kelp forest: starfish, sea urchins, snails, cup corals,” Schroeter said. “The kelp forest supports a whole host of fish. So starting the food chain from plants to invertebrates to fish, that’s the kelp forest.”

Sea stars, anemones, crabs, and jellyfish dwell in kelp forests, and sea birds swoop in to feed on small crustaceans, according to the National Oceanic and Atmospheric Administration. Commercial species including bass and rockfish use kelp for cover, and rockfish larvae take shelter in the upper water column. Fish, in turn, are food for seals, sea lions and others mammals. Sea urchins devour the kelp. And sea otters eat urchins, while lounging and playing in kelp beds.

“It’s a characteristic community,” Parnell said. “Diving in the kelp forest is like taking a walk through a terrestrial rainforest. Ten feet below the surface, it’s like you’re flying in the canopy. When you’re on the bottom, you’re shaded by this wonderful forest, and you feel protected. You feel like you’re pretty much inside, rather than outside the house."

Andrew Roe

This Norrisia norrisii snail clinging to a kelp leaf, was observed during a dive to check on the current conditions of the local kelp.

This Norrisia norrisii snail clinging to a kelp leaf, was observed during a dive to check on the current conditions of the local kelp. (Andrew Roe)

The divers returned to the surface with lustrous abalone shells, as well as sea urchins, snails and cowries. They found some unwanted things, too, including weedy clumps of sargassum, an invasive seaweed that competes with kelp.

Despite that intruder, Parnell was pleased by what he saw. Last month’s winter storms didn't wreak as much damage as he expected, and regrowth is replacing kelp lost to the warm water die-offs.

“The kelp forest is looking a lot better than it was a few years ago, I’ll tell you that much,” he said, peeling off his drysuit.

That’s not to say that San Diego’s kelp forests are out of the woods. While their condition is good, their coverage isn’t as extensive as it was before.

“There’s kelp missing in many areas that it used to be,” Parnell said. “In the areas that it’s now present, it looks very healthy and it’s growing rapidly. Fundamentally, they’re missing from some of the other areas where they typically grow. They basically haven’t recovered from the last El Nino in some areas.”

They have been spared the destruction of urchin barrens, however. That’s partly because urchins died off during the warm water episodes, as well. Although there is some urchin overgrazing on San Diego kelp beds, particularly near Point Loma, it’s not on the scale seen in Northern California, Parnell said.

“You had two different warm water events, and the kelp virtually died off,” he said. “Sea stars and urchins (also) died off.”

It’s lucky for Southern California kelp forests that their most voracious predators declined under the same conditions as the seaweed beds. But the long-term prospects for kelp in a warming world are troubling, researchers say.

Australian kelp forests off Tasmania have all but disappeared, declining by 95 percent as the water of that region has warmed faster than the global average, researchers report. Although the continent’s coral reef decline has been widely publicized, its kelp loss could be just as calamitous. San Diego’s situation is not that dire, but it may be in coming decades.

“The Tasmanian kelp story is probably the southern California kelp story over the next century,” Parnell said.

An ocean temperature time series taken from Scripps Pier over the past century shows an unsettling pattern. While ocean temperatures rise and fall in annual cycles, the average temperature began rising in the late ‘70s, creeping up by several degrees. Last year, San Diego saw some of the warmest water temperatures on record, spiking to a record 78.6 degrees last August. It’s unclear, Parnell said, if that’s simply a new record, or a new normal for the region.

Paul Dayton, a professor emeritus of oceanography at Scripps, began diving in San Diego kelp beds as a graduate student in the 1960s, and continued that research after joining the faculty in 1970.

“My first dives were one of wonder at this habitat as I floated around looking at the different structures in the kelp forest, and all the different animals,” he said.

At that time, he said, kelp forests were still recovering from strong El Ninos in the 1950s. They bounced back from those blows, but Dayton isn’t confident we can count on that in the future.

“Right now, it looks bad to me, because the ocean warming is continuing. Even though we have a break in the El Ninos, the macro kelp will be in trouble if the nutrients in the water diminish with global warming,” he said. “Right now, there’s a lot of kelp out there, so I can’t say we’re in the middle of a disaster, but it doesn’t look good for the next 10 years.”

Andrew Roe

Scripps Institution of Oceanography Researcher Ed Parnell places abalone shells on a pile of invasive Sargassum horneri sea weed, a kelp competitor, after taking a dive to check on the current conditions of the local kelp.

Scripps Institution of Oceanography Researcher Ed Parnell places abalone shells on a pile of invasive Sargassum horneri sea weed, a kelp competitor, after taking a dive to check on the current conditions of the local kelp. (Andrew Roe)

If they decline, or disappear, he said, they’ll take a host of ecological communities with them. Kelp provide food and shelter for marine animals not only while they’re growing offshore, but also after they wash away. On the beach, decomposing kelp provides food for small animals such as sand worms, arthropods and other invertebrates, which are prey for seabirds, Dayton said.

You might not care much about sand worms, he acknowledged, “but everyone loves the birds.”

Kelp paddies can also detach and float out to sea, where they provide food and shelter for rockfish larvae.

“It’s sort of a condominium of young animal people out there in the kelp paddies,” he said. “The paddies are really important to these populations for rockfish that we’re trying to recover.”

The massive algae also sink to the bottom of the sea, creating a submarine smorgasboard for deep sea creatures, he said. And they can drop into San Diego’s offshore canyons, where juvenile kelp bass and hake dine and hide in the disintegrating seaweed, Dayton said.

“If we were to lose Macrosystis, which it looks like it’s likely, it’s not only the divers that lose the structure and the beauty of our kelp forests, it’s the whole ecosystem,” Dayton warned.